Catalyst oxygen purge control apparatus and method

ABSTRACT

A catalyst oxygen purge control method may include a catalyst oxygen purge control method during a cold engine period of a catalyst oxygen purge control apparatus which includes a three way catalytic converter through which an exhaust gas combusted when air and fuel are mixed in a combustion chamber is exhausted and the exhaust gas passes, wherein the method includes determining whether a fuel cut condition of an injector which injects the fuel to the combustion chamber is satisfied, performing fuel cut of the injector when the fuel cut condition is satisfied, measuring an oxygen storage capacity of the three way catalyst, and adjusting an oxygen purge time based on the measured oxygen storage capacity.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims priority to Korean Patent Application No.10-2016-0129837 filed on Oct. 7, 2016, the entire contents of which isincorporated herein for all purposes by this reference.

BACKGROUND OF THE INVENTION Field of the Invention

Various embodiments of the present invention relates to a catalystoxygen purge control apparatus and method, and more particularly, to anapparatus and a method for adjusting an oxygen purge time after fuel-cutaccording to a degradation level of a three way catalyst.

Description of Related Art

Recently, according to increased usage of vehicles and increased trafficvolume, air pollution due to exhaust gas comes to the fore as a serioussocial problem.

Therefore, government of every country sets an emission standard ofpollutant in exhaust gas such as carbon monoxide (CO), hydrocarbon (HC),nitrogen oxide (NOx) and the like in order to regulate exhaust gas.Regulations on the exhaust gas are becoming stricter more and more.

Further, manufacturers of vehicles make a great effort to effectivelycope with the regulations on the exhaust gas which is becoming stricter.A novel vehicle is manufactured in accordance with an exhaust gasemission standard.

Particularly, in order to satisfy an exhaust gas emission standard, athree way catalyst converter in which a noble metal is immersed ismounted in an exhaust system of the vehicle to accelerate decompositionof hydrocarbon, oxidation of carbon monoxide, and reduction of nitrogenoxide.

The three way catalyst refers to a catalyst which simultaneously reactswith a hydrocarbon based compound, carbon monoxide, and nitrogen oxide(NOx) to remove these compounds and a Pt/Rh, Pd/Rh or Pt/Pd/Rh catalystis mainly used.

The three way catalyst performs a function of reducing carbon monoxideand hydrocarbon or reducing nitrogen oxide in response to change of alean (excessive oxygen) state and a rich (excessive fuel) state withrespect to an air/fuel ratio of exhaust gas.

In the meantime, in a fuel cut state, unburned air passes through thethree way catalyst so that oxygen is stored in the three way catalyst.When fuel is reinjected, a purification rate of nitrogen oxide issignificantly lowered due to the stored oxygen. In order to prevent thelowering of purification rate, an oxygen purge (O₂ purge) function whichexcessively injects the fuel at the time of respraying the fuel toconsume oxygen is performed.

In the case of a novel three way catalyst, the same oxygen purge methodis applied to fuel cut and oxygen purge regardless of before/aftercatalyst activation. Since the catalyst is not activated during the coldengine period, when oxygen is purged based on activation of catalyst,excessive hydrocarbon and carbon monoxide are emitted, so that exhaustgas purification effect is deteriorated.

The information disclosed in this Background of the Invention section isonly for enhancement of understanding of the general background of theinvention and should not be taken as an acknowledgement or any form ofsuggestion that this information forms the prior art already known to aperson skilled in the art.

BRIEF SUMMARY

Various aspects of the present invention are directed to providing acatalyst oxygen purge control apparatus and method which adjusts anoxygen purge time after a fuel-cut during the cold engine periodaccording to a degradation level of a three way catalyst to improveactual fuel efficiency of a vehicle.

Various aspects of the present invention are directed to providing acatalyst oxygen purge control apparatus including an exhaust systemwhich exhausts an exhaust gas generated in an engine, a three waycatalytic converter (TWC) which supplies a catalyst to the exhaustsystem, an oxygen sensor which detects an oxygen storage capacity (OSC)of the three way catalytic converter, a determining device whichquantitatively determines a degradation level of a catalyst using theoxygen storage capacity to determine a change control condition whichchanges an oxygen purge time of the three way catalyst, and an oxygenpurge controller which controls the catalytic converter according to thechange control condition to control the oxygen purge time.

The oxygen purge time may be controlled before activating the three waycatalyst during a cold engine period.

The change control condition may be at least one of an engine ignitiontiming, an idle revolution per minute (RPM), a CAM timing, an air/fuelratio, and an injecting condition.

Various aspects of the present invention are directed to providing acatalyst oxygen purge control method during a cold engine period of acatalyst oxygen purge control apparatus which includes a three waycatalytic converter through which an exhaust gas combusted when air andfuel are mixed in a combustion chamber is exhausted and the exhaust gaspasses, the method including determining whether a fuel cut condition ofan injector which injects the fuel to the combustion chamber issatisfied, performing fuel cut of the injector when the fuel cutcondition is satisfied, measuring an oxygen storage capacity of thethree way catalyst, and adjusting an oxygen purge time based on themeasured oxygen storage capacity.

One criteria of the cold engine during the cold engine period may bethat an exhaust gas temperature at a front end portion of the three waycatalytic converter is lower than approximately 400 degrees and a timeis before activation of the three way catalyst.

A criteria of the cold engine during the cold engine period may bebefore approximately 200 seconds after starting the engine, and bebefore the activation of the three way catalyst.

The oxygen purge time may be determined by the oxygen storage capacityof the three way catalyst.

As the oxygen storage capacity is small, the oxygen purge time may beincreased.

The oxygen storage capacity may be measured using a chemical adsorptionmethod, a simulation activation evaluation device, an engine, or avehicle.

The oxygen storage capacity may be determined in accordance with adegradation level of the three way catalyst.

As the degradation level of the three way catalyst is increased, theoxygen storage capacity may be reduced.

The oxygen storage capacity may be linearly inversely proportional tothe degradation level of the three way catalyst.

According to an exemplary embodiment of the present invention, acatalyst oxygen storage characteristic during the cold engine period isreflected to adjust an oxygen purge time, to minimize generation ofexhaust gas. Further, an oxygen purge time during the cold engine periodis shortened during the cold engine period to further improve fuelefficiency.

The methods and apparatuses of the present invention have other featuresand advantages which will be apparent from or are set forth in moredetail in the accompanying drawings, which are incorporated herein, andthe following Detailed Description, which together serve to explaincertain principles of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic block diagram of a catalyst oxygen purge controlapparatus according to an exemplary embodiment of the present invention.

FIG. 2 is a flowchart illustrating a catalyst oxygen purge controlmethod according to an exemplary embodiment of the present invention.

FIG. 3 is a graph illustrating an EM exhaust behavior when a catalystoxygen purge of a 4 Kmile degraded product is performed during the coldengine period according to an exemplary embodiment of the presentinvention.

FIG. 4 is a graph illustrating an EM exhaust behavior when a catalystoxygen purge of a 150 Kmile degraded product is performed during thecold engine period according to an exemplary embodiment of the presentinvention.

FIG. 5 is a graph illustrating an EM exhaust behavior when a catalystoxygen purge of a 4 Kmile degraded product is performed during the warmengine period according to an exemplary embodiment of the presentinvention.

FIG. 6 is a graph illustrating an EM exhaust behavior when a catalystoxygen purge of a 150 Kmile degraded product is performed during thewarm engine period according to an exemplary embodiment of the presentinvention.

FIG. 7 is a graph illustrating an oxygen storage capacity of a catalystaccording to a catalyst degradation level according to an exemplaryembodiment of the present invention.

FIG. 8 is a graph illustrating an oxygen purge time according to anoxygen storage capacity of a catalyst according to an exemplaryembodiment of the present invention.

It should be understood that the appended drawings are not necessarilyto scale, presenting a somewhat simplified representation of variousfeatures illustrative of the basic principles of the invention. Thespecific design features of the present invention as disclosed herein,including, for example, specific dimensions, orientations, locations,and shapes will be determined in part by the particular intendedapplication and use environment.

In the figures, reference numbers refer to the same or equivalent partsof the present invention throughout the several figures of the drawing.

DETAILED DESCRIPTION

Reference will now be made in detail to various embodiments of thepresent invention(s), examples of which are illustrated in theaccompanying drawings and described below. While the invention(s) willbe described in conjunction with exemplary embodiments, it will beunderstood that the present description is not intended to limit theinvention(s) to those exemplary embodiments. On the contrary, theinvention(s) is/are intended to cover not only the exemplaryembodiments, but also various alternatives, modifications, equivalentsand other embodiments, which may be included within the spirit and scopeof the invention as defined by the appended claims.

Further, in exemplary embodiments, since like reference numeralsdesignate like elements having the same configuration, a one exemplaryembodiment is representatively described, and in other exemplaryembodiments, only a configuration different from one exemplaryembodiment will be described.

It is noted that the drawings are schematic and are not dimensionallyillustrated. A relative size and a ratio of parts in the drawings may beexaggerated or reduced for clarity and convenience in the drawings andan arbitrary size is just illustrative but is not restrictive. Inaddition, the same reference numerals designate the same structures,elements, or parts illustrated in the two or more drawings to exhibitsimilar characteristics. It will be understood that when an element isreferred to as being “on” or “over” another element, it can be directlyon the other element or intervening elements may also be present.

An exemplary embodiment of the present invention indicates an exemplaryembodiment of the present invention. As a result, various modificationsof the drawings are expected. Accordingly, the exemplary embodiment isnot limited to a specific form of the illustrated region, and forexample, includes a modification of a form by manufacturing.

Hereinafter, a catalyst oxygen purge control apparatus according to anexemplary embodiment of the present invention will be described withreference to FIG. 1.

FIG. 1 is a schematic block diagram of a catalyst oxygen purge controlapparatus according to an exemplary embodiment of the present invention.

Referring to FIG. 1, a catalyst oxygen purge control apparatus includesan exhaust system 120, a three way catalytic converter (TWC) 130, anoxygen sensor 131, a determining device 150, and an oxygen purgecontroller 140.

The exhaust system 120 emits exhaust gas generated in an engine 110 andthe three way catalytic converter 130 supplies a catalyst to the exhaustsystem 120. The three way catalytic converter 130 includes an oxygensensor 131 which detects an oxygen storage capacity of the three waycatalytic converter 130.

Examples of the engine 110 include a continuous variable valve timing(CVVT) engine, a double overhead camshaft (DOHC) engine, a continuousvalve timing (CVT) engine, a gasoline direct injection (GDI) engine, anda multipoint injection (MPI) engine using gasoline as a fuel. Inaddition to the above-mentioned gasoline engine, an exemplary embodimentof the present invention may be applied to an engine using diesel asfuel and an engine using gas as a fuel.

The exhaust system 120 may be configured by an exhaust muffler whichemits an exhaust gas generated in the engine, but also may be configuredby a manifold or a catalyst converter.

The three way catalytic converter 130 includes a catalyst which performsoxygen and reduction reaction with the exhaust gas and a heater whichheats the catalyst.

The oxygen sensor 132 detects an oxygen storage capacity of the threeway catalytic converter 130 to provide the detected oxygen storagecapacity information to the determining device 150.

The determining device 150 quantitatively determines a degradation levelof the catalyst using the oxygen storage capacity to determine a changecontrol condition to change an oxygen purge time of the three waycatalyst.

As a mileage is increased, a performance of the catalyst is graduallydeteriorated, which is referred to as catalyst degradation. The catalystdegradation may be generated by chemical inactivation or thermalinactivation. A major cause of degradation of a gasoline catalyst isthermal degradation due to exposure to a high temperature. Thedegradation results in increase of activation temperature (LOT,Light-Off Temperature) and reduction of conversion efficiency.

The oxygen purge controller 140 controls the catalytic converter 130 inaccordance with the change control condition to control the oxygen purgetime. The oxygen purge time may be controlled before activating thethree way catalyst during the cold engine period and the change controlcondition may be at least one of an engine ignition timing, an idlerevolution per minute (RPM), a CAM timing, an air/fuel ratio, and aninjecting condition. Among these, a most influential condition is theengine ignition timing and the air/fuel ratio.

FIG. 2 is a flowchart illustrating a catalyst oxygen purge controlmethod according to an exemplary embodiment of the present invention.

Referring to FIG. 2, a catalyst oxygen purge control method according toan exemplary embodiment of the present invention is a catalyst oxygenpurge control method during the cold engine period of a catalyst oxygenpurge control apparatus which includes a three way catalytic converterthrough which an exhaust gas combusted when air and fuel are mixed in acombustion chamber is exhausted and the exhaust gas passes. First, it isdetermined whether a fuel cut condition of an injector which injects thefuel to the combustion chamber is satisfied in step S201.

Next, when the fuel cut condition is satisfied, the fuel cut of theinjector is performed in step S202.

Next, an oxygen storage capacity of the three way catalyst is measuredin step S203. The oxygen storage capacity may be measured using achemical adsorption method, a simulation activation evaluation device,an engine, or a vehicle. Further, the oxygen storage capacity may bedetermined in accordance with a degradation level of the three waycatalyst. As the degradation level of the three way catalyst isincreased, the oxygen storage capacity is reduced. Further, the oxygenstorage capacity may be linearly inversely proportional to thedegradation level of the three way catalyst.

Next, an oxygen purge time is adjusted based on the measured oxygenstorage capacity in step S204.

In the instant case, a criterion of the cold engine during the coldengine period is that an exhaust gas temperature at a front end portionof the three way catalytic converter is lower than approximately 400degrees and a time is before activation of the three way catalyst.Further, the time may be before approximately 200 seconds after startingthe engine, and may be before the activation of the three way catalyst.

Further, the oxygen purge time may be determined by the oxygen storagecapacity of the three way catalyst. The smaller the oxygen storagecapacity is, the longer the oxygen purge time is.

In the meantime, the oxygen storage capacity may be measured after afuel cut in the oxygen purge time adjusting step S204 and then may bechanged. However, there may be a deviation of a measurement value.Therefore, an oxygen storage capacity which is measured in apredetermined condition during general operation to be updated may beused.

Further, the oxygen storage capacity may be measured in the fuel cutstep S202 or under a fixed speed condition.

FIG. 3 is a graph illustrating an EM exhaust behavior when a catalystoxygen purge of a 4 Kmile degraded product is performed during the coldengine period according to an exemplary embodiment of the presentinvention and FIG. 4 is a graph illustrating an EM exhaust behavior whena catalyst oxygen purge of a 150 Kmile degraded product is performedduring the cold engine period according to an exemplary embodiment ofthe present invention.

Referring to FIG. 3, during the cold engine period when a three waycatalyst exhaust temperature is approximately 400 degrees or lowerbefore approximately 200 seconds after starting the engine, a lambdavalue of a front end portion of the three way catalytic converter of the4 Kmile degraded product, that is, an air/fuel ratio is lowered at thetime of oxygen purge. An amount of exhausted hydrocarbon and nitrogenoxide which is measured at an exit WCC of the three way catalyticconverter is small. Further, referring to FIG. 4, during the cold engineperiod when a three way catalyst exhaust temperature is approximately400 degrees or lower before approximately 200 seconds after starting theengine, in the 150 Kmile degraded product, an emission amount ofexhausted hydrocarbon and nitrogen oxide is increased at the time ofoxygen purge.

As illustrated in FIG. 3 and FIG. 4, in the case of the 4 Kmile degradedproduct which is a new product, an EM exhaust characteristic during thecold engine period is low. Further, in the case of a new product, theoxygen purge time is shortened, so that the fuel efficiency may befurther improved.

FIG. 5 is a graph illustrating an EM exhaust behavior when a catalystoxygen purge of a 4 Kmile degraded product is performed during the warmengine period according to an exemplary embodiment of the presentinvention and FIG. 6 is a graph illustrating an EM exhaust behavior whena catalyst oxygen purge of a 150 Kmile degraded product is performedduring the warm engine period according to an exemplary embodiment ofthe present invention.

Referring to FIG. 5 and FIG. 6, during the warm engine period when athree way catalyst exhaust temperature is approximately 400 degrees orhigher after approximately 200 seconds after starting the engine,hydrocarbon is not exhausted but a large amount of nitrogen oxide isexhausted. As illustrated in FIG. 5 and FIG. 6, during the warm engineperiod, since it is observed that the 4 Kmile degraded product and the150 Kmile degraded product exhaust a similar amount of nitrogen oxide,it is difficult to shorten oxygen purge time.

FIG. 7 is a graph illustrating an oxygen storage capacity of a catalystaccording to a catalyst degradation level according to an exemplaryembodiment of the present invention.

Referring to FIG. 7, it is understood that as compared with the 4 Kmiledegraded product, an oxygen storage capacity of the 150 Kmile degradedproduct is small. For example, in the case of a gasoline vehicle with1.4 liter engine, it is understood that an oxygen storage capacity of athree-way catalyst of a 4 Kmile degraded product is approximately 1700mg and an oxygen storage capacity of a three-way catalyst of a 150 Kmiledegraded product is approximately 940 mg. The oxygen storage capacity islinearly inversely proportional to a degradation level of the three waycatalyst.

FIG. 8 is a graph illustrating an oxygen purge time according to anoxygen storage capacity of a catalyst according to an exemplaryembodiment of the present invention.

Referring to FIG. 8, as compared with the 4 Kmile degraded product, theoxygen purge time of the 150 Kmile degraded product is increased. Thatis, as the oxygen storage capacity is reduced, the oxygen purge time isincreased after the fuel cut. In the instant case, the oxygen storagecapacity is linearly inversely proportional to the oxygen purge time.For example, in the case of a gasoline vehicle with 1.4 liter engine, anoxygen purge time of a three-way catalyst of a 4 Kmile degraded productis adjusted to approximately 10 seconds and an oxygen purge time of athree-way catalyst of a 150 Kmile degraded product is adjusted toapproximately 20 seconds.

As described above, according to the exemplary embodiment of the presentinvention, the catalyst oxygen storage characteristic during the coldengine period is reflected to adjust the oxygen purge time, minimizingthe exhaust gas.

Further, the oxygen purge time is shortened during the cold engineperiod, further improving fuel efficiency.

The foregoing descriptions of specific exemplary embodiments of thepresent invention have been presented for purposes of illustration anddescription. They are not intended to be exhaustive or to limit theinvention to the precise forms disclosed, and obviously manymodifications and variations are possible in light of the aboveteachings. The exemplary embodiments were chosen and described toexplain certain principles of the invention and their practicalapplication, to enable others skilled in the art to make and utilizevarious exemplary embodiments of the present invention, as well asvarious alternatives and modifications thereof. It is intended that thescope of the invention be defined by the Claims appended hereto andtheir equivalents.

1. A catalyst oxygen purge control apparatus, comprising: an exhaustsystem which exhausts an exhaust gas generated in an engine; a three waycatalytic converter (TWC) which supplies a catalyst to the exhaustsystem; an oxygen sensor which detects an oxygen storage capacity (OSC)of the three way catalytic converter; a determining device which isconfigured to quantitatively determine a degradation level of thecatalyst using the oxygen storage capacity to determine a change controlcondition which changes an oxygen purge time of the three way catalyst;and an oxygen purge controller which controls the catalytic converteraccording to the change control condition to control the oxygen purgetime.
 2. The catalyst oxygen purge control apparatus of claim 1, whereinthe oxygen purge time is configured to be controlled before activatingthe three way catalyst during a cold engine period.
 3. The catalystoxygen purge control apparatus of claim 1, wherein the change controlcondition is at least one of an engine ignition timing, an idlerevolution per minute (RPM), a CAM timing, an air/fuel ratio, and aninjecting condition. 4-12. (canceled)